Differential pressure gage with semiconductor type strain gage elements measures rapidly changing pressure. Output of the strain gage elements is a dc voltage that is directly proportional to the pressure difference being measured

Weber, H. S.

English

NASA Technical Reports Server

Limiting 
Device 
Inlet
Inlet 
Chamber B 
iws 
September 1965	 Brief 65-10285 
NASA TECH 
NASA Tech Briefs are issued by the Technology Utilization Division to summarize specific 
technical innovations derived from the space program. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia, 22151. 
Differential Pressure Gauge Has Fast Response 
Gauge Housing	 Piston Face Plate 
Chamber A 
The problem: To design a differential pressure 
gauge that will reliably measure rapidly changing pres-
sures as low as 10-3 mm Hg. A thermocouple gauge 
will measure these small pressures but has the slow 
half-time of about 5 seconds. An ionization gauge has 
the range and rapid response desired but causes de-
composition of organic fluids and the gauge quickly 
becomes contaminated and unreliable. 
The solution: A differential pressure gauge using 
semiconductor-type strain gauge elements. Output of 
the strain gauge elements is a dc voltage that is di-
rectly proportional to the pressure difference being 
measured.
How it's done: The differential pressure gauge has 
two chambers (A and B) separated by a bellows and 
piston. The bellows is attached between the piston 
face plate and gauge housing in one chamber and the 
piston rod connects with a limiting or damping device 
in the other chamber. Between the two, a flat, thin 
strip of flexible metal is mounted on one end to the 
gauge housing and on the other end to the piston rod. 
Cemented on this metal strip are four semiconductor-
type strain gauge elements wired together in a Wheat-
stone bridge arrangement. A pressure difference be-
tween chamber A and chamber B is transmitted to the 
strain gauge elements b y the action of the bellows 
(continued overkaf) 
This document was prepared under the sponsorship of the National 
Aer.rtautics and Space Administration. Neither the United States 
Goernment nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19650000283 2020-03-11T17:20:49+00:00Z
and piston flexing the thin metal strip. This flexing 
causes a change in the resistance of the elements that 
alters an applied dc voltage directly proportional to 
the difference in the pressures of the two chambers. 
The limiting device on one end of the piston rod 
damps the motion of the piston and belows under high 
pressure differences between the chambers. 
Notes: 
I. This gauge has rapid response and may be made of 
materials that are inert to most fluids. 
2. Accuracy and sensitivity of the gauge is governed 
by the semiconductor strain elements used.
3. Inquiries concerning this innovation may be di-
rected to:
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama, 35812 
Reference: B65-10285 
Patent status: NASA encourages commercial use 
of this innovation. No patent action is contemplated 
by NASA.
Source: Harold S. Weber of Armour 
Research Foundation under 
contract to Marshall Space 
Flight Center 
(M-FS-358) 
Brief 65-10285	 Category 05


Differential pressure gauge has fast response

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